How come in Alaska during summer temperatures can reach 25 degrees Celsius @ 300m but in does melt the glacier

Question

How come in Alaska during summer temperatures can reach 25 degrees Celsius @ 300m but in does melt the glacier

Answer 1

When we say temperatures can reach 25 degrees C, we talk about the air's temperature. Air has a very low heat capacitance (around 0.001 J/Kg/K and a Kg of air takes almost a cubic meter!) and a very low thermal conductivity (0.024W/m/K).

It is therefor possible for air temperature to differ quite alot from that of the ice.

If you measured the air temperature near the ice (say 1 mm away), you'd see air close to 0C, while 5 centimeters away, temperature would reach 25C.

The rate of heat flow towards the ice is therefor only:

0.024/0.05*25=12W/m^2.

Melting ice costs about 336 KJ/Kg of heat, so if you have a block of 1m^3 ice, which weighs about 1 ton, it would take 336,000 KJ of heat,  which at a rate of 12 W would be obtained in 28,000,000 seconds, which are 324 days....

So you see that heat conductance through air is a very slow way to melt glaciers. Without sunlight or strong winds, air could remain 25 degrees hotter than the glacier for days with no significant impact.

Answer 2

the glacier melts during the summer months but due to its altitude it doesn't get as warm as you might think.

Answer 3

Mother Nature's magic!

Answer 4

Ah but it does!

However not as quick as you would expect as the white of the ice reflects the sunlight.